I have some idea that the intervals between aren't the same each time, but there should be some pattern to them, much like we have a pattern for eclipses here on earth. But we only have three bodies to deal with and the Ballybran system would have five!

I suppose I'll have to use my knowledge of earth-moon eclipses to reconstruct the Ballybran system then?

I don't think it does give a stated time, but it does state "the passover storms of" a given year, so it doesn't seem like they could be more often than once a year. If it were more often than that, they would have had to say "the passover storms of early" whatever year. Could be less often than a year, though.

Considering the number of astronomical bodies involved in the alignments I would expect a 'passover' periood to be in excess of a 'year'; and even then there would be major and minor passovers according to whether ALL the bodies were lined up, or only nearly all of them. The amplitude of the storms would then be affected by which of the bodies was out of line.

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